1 files changed, 42 insertions, 2 deletions

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index b0f218797630..59e1d15c4d02 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -197,6 +197,9 @@ MODULE_PARM_DESC(macaddr, "FEC Ethernet MAC address");
 #endif
 #endif /* CONFIG_M5272 */
 
+/* Minimum TX ring size when using NETIF_F_SG */
+#define TX_RING_SIZE_MIN_SG (2 * (MAX_SKB_FRAGS + 1))
+
 /* Interrupt events/masks. */
 #define FEC_ENET_HBERR	((uint)0x80000000)	/* Heartbeat error */
 #define FEC_ENET_BABR	((uint)0x40000000)	/* Babbling receiver */
@@ -476,7 +479,7 @@ static int fec_enet_txq_submit_skb(struct sk_buff *skb, struct net_device *ndev)
 	unsigned int index;
 	int ret;
 
-	if (fec_enet_get_free_txdesc_num(fep) < MAX_SKB_FRAGS + 1) {
+	if (fec_enet_get_free_txdesc_num(fep) < fep->tx_min) {
 		dev_kfree_skb_any(skb);
 		if (net_ratelimit())
 			netdev_err(ndev, "NOT enough BD for SG!\n");
@@ -2471,7 +2474,22 @@ static void fec_poll_controller(struct net_device *dev)
 }
 #endif
 
-#define FEATURES_NEED_QUIESCE NETIF_F_RXCSUM
+static netdev_features_t fec_fix_features(struct net_device *ndev,
+	netdev_features_t features)
+{
+	struct fec_enet_private *fep = netdev_priv(ndev);
+
+	/*
+	 * NETIF_F_SG requires a minimum transmit ring size.  If we
+	 * have less than this size, we can't support this feature.
+	 */
+	if (fep->tx_ring_size < TX_RING_SIZE_MIN_SG)
+		features &= ~NETIF_F_SG;
+
+	return features;
+}
+
+#define FEATURES_NEED_QUIESCE (NETIF_F_RXCSUM | NETIF_F_SG)
 
 static int fec_set_features(struct net_device *netdev,
 	netdev_features_t features)
@@ -2496,6 +2514,17 @@ static int fec_set_features(struct net_device *netdev,
 			fep->csum_flags &= ~FLAG_RX_CSUM_ENABLED;
 	}
 
+	/* Set the appropriate minimum transmit ring free threshold */
+	if (features & NETIF_F_SG) {
+		fep->tx_min = MAX_SKB_FRAGS + 1;
+		fep->tx_stop_threshold = FEC_MAX_SKB_DESCS;
+		fep->tx_wake_threshold = (fep->tx_ring_size - fep->tx_stop_threshold) / 2;
+	} else {
+		fep->tx_min = 1;
+		fep->tx_stop_threshold = 1;
+		fep->tx_wake_threshold = 1;
+	}
+
 	/* Resume the device after updates */
 	if (netif_running(netdev) && changed & FEATURES_NEED_QUIESCE) {
 		fec_restart(netdev);
@@ -2520,6 +2549,7 @@ static const struct net_device_ops fec_netdev_ops = {
 #ifdef CONFIG_NET_POLL_CONTROLLER
 	.ndo_poll_controller	= fec_poll_controller,
 #endif
+	.ndo_fix_features	= fec_fix_features,
 	.ndo_set_features	= fec_set_features,
 };
 
@@ -2606,6 +2636,16 @@ static int fec_enet_init(struct net_device *ndev)
 		fep->csum_flags |= FLAG_RX_CSUM_ENABLED;
 	}
 
+	if (ndev->features & NETIF_F_SG) {
+		fep->tx_min = MAX_SKB_FRAGS + 1;
+		fep->tx_stop_threshold = FEC_MAX_SKB_DESCS;
+		fep->tx_wake_threshold = (fep->tx_ring_size - fep->tx_stop_threshold) / 2;
+	} else {
+		fep->tx_min = 1;
+		fep->tx_stop_threshold = 1;
+		fep->tx_wake_threshold = 1;
+	}
+
 	ndev->hw_features = ndev->features;
 
 	fec_restart(ndev);